After the manufacturing of integrated circuits (ICs), such as a computer processors, multiple IC devices are placed onto a burn-in-board (“BIB”) and tested at stressed conditions at elevated temperatures for a specific time period in a “burn-in” test. A burn-in test will reveal infant mortality failures of an IC by thermally and electrically stressing each device with accompanying functional testing to measure output signals from the device-under-test (“DUT”). In fabrication and manufacturing of an IC device, the processes can introduce flaws in any one of several physical mechanisms of the device, which can lead to ultimate failure. Such a flaw can be directly affected by a burn-in program so as to fail prematurely. The ICs that fail a result of fabrication errors, and ICs that fail early in the test procedure indicate a much earlier expected failure than if the IC was used under actual operating conditions. Burn-in tests also expose ICs that do not have apparent manufacturing flaws but would nevertheless fail during the expected life of the device.
DUTs are loaded onto a BIB, which is a test board that are typically larger than a common computer add-on board. The BIB is placed into a Burn-In oven or a chamber that subjects the devices to increased temperature and voltage conditions. The devices are then exercised under a variety of stresses while verifying that the correct stimuli is applied by monitoring one output pin of each DUT without removing them from the BIB. The DUTs are electrically stressed by connected terminals on the devices to signal supply pins of a test system, where increased voltage and elevated current are supplied to the devices. The test system drives the test patterns into all of the DUTs mounted on the BIB. The electrical stress tests can be performed on each input/output (I/O) of the devices. Devices that fail to operate normally during the burn-in test are declared defective and are discarded based on results of subsequent testing. Further, a burn-in test can determine under what temperature ranges different devices can be expected to reliably operate.
Most conventional BIBs have electronics and wiring to connect signal drivers and signal receivers to the DUTs. The system may have a driver board outside the oven that is operably connected to the BIB through a backplane board. The driver board contains components including traces for power, ground, and control signals to and from the BIB.
The BIB is used to stress the devices after the devices are tested on a load board. ICs that pass the burn-in test go back to a load board for further tests. The ICs that pass the final tests will be sold. For the burn-in test, typically multiple devices are placed on each BIB, and the BIB is placed into an oven or chamber that is heated, for example heated up to 125° C. The devices are tested at a higher voltage than normal operating conditions. On every device, the burn-in tests exercise not only the core of the device but also the I/Os of the device by loading the device with resistors. FIG. 1 illustrates a typical conventional BIB. BIB 10 includes twenty-four burn-in sockets 12 that each receive a DUT (not shown) for testing. BIB also provides power conductors, signal conductors, and ground conductors (not shown) to couple the DUTs and the BIB to a test system through contacts 14. Each I/O terminal of a DUT is coupled to one or more resistors attached to a BIB.
The loading of the device I/Os is usually performed using one or two resistors on each output of a DUT. The two resistors can be a resistor to ground and a resistor to power. If the output goes high, the pull-down resistor will load it and the current will flow through it to ground. If the output goes low, the pull-up resistor will load it and drive the current to the output of the device. If a DUT has two hundred outputs, and each output has two resistors, then the BIB requires four hundred resisters attached to it in order to test each DUT. If a single BIB can hold fifty DUTs simultaneously, the BIB requires twenty thousand load resistors in addition to other components.
An inherent problem with convention methods for burn-in testing of ICs are the production costs. Burn-in test systems require ovens or chambers large enough to receive multiple BIBs, and each BIB costs thousands of dollars. A BIB should contain as many DUTs as possible in order to reduce production costs, but the way current devices and BIBs are designed there are too many external components required for each DUT, which increases costs. Further, because of size limitations of the system components, and the circuitry necessary to test the ICs, fewer devices can be placed onto a BIB for testing, which also increases production costs.